1. health and fitness
2. disease

FARM & ACREAGE
NEBLINE
May 2015 • Page 4
Using Corn Growing Degree Day Tool
temperature range. GDD are
important for agriculture since
they can be directly related to
plant growth and development
stages. GDD are sometimes also
called growing degree units
(GDU), heat units or thermal
time. There are many ways to
calculate GDD. The Corn GDD
tool uses the 86/50 method (also
called Modified GDD or Corn
GDD) since it only allows GDD
to be accumulated when temperature conditions are optimal for
corn development (above 50°F
but below 86°F).
Tyler Williams
Extension Educator
About the Tool
The Corn Growing Degree
Day (GDD) decision support
online tool was developed by
the Useful to Usable (U2U)
project, which is geared towards
improving the resilience and
profitability of U.S. farms in the
Corn Belt. To access the Corn
GDD tool and other tools from
U2U, go to http://agclimate4u.org.
The Corn GDD tool puts
current conditions into a 30-year
historical perspective and
offers trend projections (based
on climatology) through the
end of the calendar year. GDD
projections, combined with
analysis of historical analog data,
can help you make decisions
about seasonal climate risks,
activity planning and marketing
decisions. While this tool is not
meant to be a crystal ball, data
and information derived from
the tool can be used to make
helpful inferences about current
conditions, especially when
combined with personal experience and localized knowledge.
Growing Degree Days
(GDD) are a measure of heat
accumulation within a specified
Using the Tool
The Corn GDD tool can
provide decision support on
a variety of issues throughout
the entire growing season by
integrating current weather data,
historical climate data and farmspecific crop information into an
easy-to-use tool. The tool allows
you to select your location, enter
corn maturity length, planting
date and adjust freeze thresholds.
Before your crop is even
planted, you can start using
Corn GDD information. Test
the effects of different seed
maturity ratings and planting
dates on crop growth milestones,
informing your early seed
purchases. Use historical freeze
data to assess the risk of frost
Example data from Corn Growing Degree Day online tool.
damage at planting and harvest
time, helping you determine
when you might want to plant.
The Corn GDD tool can
also help you assess risk and
adjust practices during the
season. In the case of delayed
planting or re-planting, you can
use Corn GDD data to decide
if a shorter-season hybrid is
needed to increase the chance of
reaching crop maturity before
the first fall frost. The Corn
GDD tool can also be used to
track current corn development
and anticipate upcoming corn
growth milestones for spraying
or side-dressing nitrogen. When
presented with your farming
decisions, climate is just one
of many important factors you
need to consider. The Corn GDD
tool takes the guesswork out of
assessing your climate-related
risks.
Dead branches in trees can
have many causes, but canker
infections are one of the most
damaging and difficult to
manage. The term “canker” is
defined as a dead section of a
tree or shrub’s bark. Both fungi
and bacteria pathogens can
cause canker infections on twigs,
stems, tree limbs and trunks.
The pathogen invades the plant,
growing between the plant’s
bark and its inner wood, killing
the living portion of the outer
bark. Death of the bark limits the
plant’s ability to transport water,
absorbed by the root system, into
branch tissues.
Canker Symptoms
In deciduous trees and
shrubs, early symptoms of a
canker infection can sometimes
be seen as leaves wilt from a
lack of water. Closely inspect
the stem or branch, especially in
meaning each type of pathogen
attacks a certain host plant, or
group of plants. But unfortunately, almost every plant
is subject to some type of
canker-causing pathogen. Below
are some of the canker diseases
commonly affecting trees in
Nebraska.
William Jacobi, Colorado State University, Bugwood.org
Sarah Browning
Extension Educator
William Jacobi, Colorado State University, Bugwood.org
Managing Cankers in Landscape Plants
Deciduous Trees
Some canker infections
can be easy to spot, like
this Thyronectria canker on
honeylocust.
Other canker infections are
much harder to see, like this
Cytospora canker on alder.
Cracks around dead bark and
white streaks of dried sap
indicate canker in evergreens.
thin-barked plants, looking for a
dark or discolored area of bark.
Discolored bark may be darker
than normal; black or dark
brown, reddish-brown, orangebrown; or lighter than normal,
light tan to white. The canker, or
dead section of bark, is usually
slightly sunken below the level of
healthy bark.
On older trees with thick
bark, cankers can be harder to
find, but often cracks develop
around the dead section. Look
for cracked and discolored
sections of bark at the base of
any dead branches.
In evergreens, a common
symptom of a canker infection
is resin or sap leaking from the
canker. As the resin dries, it turns
white. Look for streaks of white
resin on the tree’s trunk, and
try to pinpoint where they are
coming from to find the canker.
Eventually, in both
deciduous and evergreen plants,
canker infection results in dead
and dying branches.
Common Canker
Diseases Found in
Nebraska
Canker-causing fungi and
bacteria are host specific,
Master Conservationist
Entries Due June 1
The Master Conservationist program was
established in 1983 to recognize those who have
excelled in soil and/or water conservation. A
winner will be selected from each of the three
established categories: production
agriculture, community and youth.
Deadline for nominations is
June 1. More information and
submission forms can be found
at http://owh.com/community/
master-conservationist-awards.
• Botryosphaeria canker —
commonly found on dogwood.
Affects over 100 species of
woody trees and shrubs.
Infections occur through
wounds, lenticels and cracks in
the bark.
• Cytospora canker — apple,
ash, aspen, birch, cottonwood,
elm, maple, peach and willow.
Infects only through wounds or
other openings in the bark.
• Nectria canker —
crabapple, pear, quaking aspen,
black walnut, American elm,
red maple, sugar maple, linden
and red oak. Pruning wounds
are common points of entry.
see CANKERS on page 5
Tractor Safety Courses for Youth 14–15
The Nebraska LEAD Program began 33 years ago to
develop agricultural leaders for Nebraska’s future
generations. Application deadline for LEAD Group 35
is June 15. Applicants generally are ages 25–55 and
should be actively involved in farming, ranching or
business closely related to agriculture.
More information at http://lead.unl.edu
For application materials and/or further information,
call 402-472-6810 or email sgerdes2@unl.edu.
All youth 14 or 15 years of age who work on a
farm or ranch other than his/her parents is required
to be certified through a tractor safety course.
Nebraska Extension Tractor Safety Courses will
be offered at seven locations in Nebraska during
May and June. A training will be held in Lincoln at
the Lancaster Event Center on June 4–5.
Pre-registration is strongly encouraged at least
one week in advance. Cost is $60. Registration form
is online at http://kearney.unl.edu. Mail to Tyler
Williams, Nebraska Extension in Lancaster County,
444 Cherrycreek Road, Suite A, Lincoln NE 68528.
For more information, call 402-441-7180.